Hub transmission for a bicycle

Abstract

 The invention relates to a hub transmission for a bicycle comprising: a hub axle (1); a driver (2) rotatably supported by the hub axle (1); a hub shell (3) rotatably supported by the hub axle (1); a power transmission mechanism (4) disposed between the driver (2) and the hub shell (3) for communicating rotational power from the driver (2) to the hub shell (3) through a plurality of power transmission paths; and a shift mechanism (5) for selecting one of the plurality of power transmission paths; wherein the power transmission mechanism (4) comprises a plurality of planetary gear mechanisms (6, 7, 8, 9, 10). The invention is characterized in that a planetary gear carrier (31) of a downstream planetary gear mechanism meshes with planetary gears (44) of an upstream planetary gear mechanism. The downstream planetary gear mechanism comprises more than one sun gear.

Description

[0001] The present invention relates to a hub transmission for a bicycle according to the preamble of claim 1. A hub transmission of this kind is known for example from DE 10 2004 011 052 A1.

[0002] Internally mounted multi-speed hub transmissions are mounted to the rear wheel of a bicycle and allow a rider of the bicycle to select different gear ratios to change the pedalling force. Typically a hub transmission comprises a hub axle that is mounted to the bicycle frame. The hub axle rotatably supports a driver for transmitting a pedalling force to the hub transmission through a sprocket and a chain. The hub transmission further comprises a hub shell which is likewise rotatably supported by the hub axle.

[0003] The hub shell accommodates a power transmission mechanism which is disposed between the driver and the hub shell for transmitting rotational power from the driver to the hub shell. The power transmission mechanism provides a plurality of power transmission paths with different gear ratios that can be selected by means of a shift mechanism, wherein each power transmission path typically produces a specific gear ratio. To establish the plurality of power transmission paths the power transmission mechanism ordinarily comprises several planetary gear mechanisms.

[0004] Current internal hub transmissions are designed to provide 10 or more speed stages. The hub transmission according to DE 10 2004 011 052 A1 allows a selection between 9 speed stages which are provided by a plurality of planetary gear mechanisms. The known hub transmission comprises three planetary gear mechanisms that allow the combination of three speed stages with another five speed stages, for a total of nine speed stages with a gear ratio of 340%. The hub transmission includes a first planetary gear mechanism comprising a first sun gear that is non-rotatably mounted to the hub axle, a first planetary gear rotatably supported by a first planetary gear carrier and a first ring gear. The first planetary gears are disposed between the first sun gear and the first ring gear and mesh with the same.

[0005] A second planetary gear mechanism includes a second sun gear which is arranged on the first planetary gear carrier. Second planetary gears are mounted on the first ring gear.

[0006] A third planetary gear mechanism is formed similar to the second planetary gear mechanism and includes a third sun gear mounted on the first planetary gear carrier. The third sun gear meshes with third planetary gears each of which is non-rotatably joined to the respective second planetary gears. Thereby a two-step planetary gear is formed. The third planetary gears mesh with a second ring gear to transmit the torque of the third planetary gear mechanism to the second planetary gear mechanism.

[0007] The shifting mechanism of this hub transmission comprises a pawl carrier which allows coupling the driver selectively with components of the respective planetary gear mechanisms to produce different gear ratios. To this end the pawl carrier comprises a plurality of controllable pawls, namely six pawls that are actuated by means of three shifting cams.

[0008] The arrangement of the two-step planetary gear on the first ring gear in combination with the second ring gear that meshes with the two-step planetary gears, leads to a pile type of internal hub transmission. Since the second ring gear overlaps the other components of the three planetary gear mechanisms, the diameter of the second ring gear and, thus, the diameter of the internal hub transmission is increased. Moreover, the pile type construction of the internal hub transmission leads to an increased total weight of the hub.

[0009] As described above, the second and third sun gears are each mounted on the first planetary gear carrier. Therefore, the second and third sun gears each rotate together with the first planetary gear carrier around the hub axle. In particular, the power transmission path for speed stages 8 and 9 comprises the driver, the sixth pawl and the first planetary gear carrier wherein the first planetary gears rotate around the first sun gear. The power transmission path further comprises the first ring gear, the second ring gear, the first pawl, the pawl connecting the power transmission with the hub shell and the hub shell. In speed stage 8, the third planetary gear rotates around the third sun gear and in speed stage 9 the second planetary gear rotates around the second sun gear.

[0010] Due to this differential rotational type of the planetary gear mechanism the power transmission paths are complicated, in particular the power transmission paths for speed stages 8 and 9 which therefore inefficiently transmit power.

[0011] A similar hub transmission is known from DE 197 20 796 A1 which discloses a multiple speed hub having a plurality of planetary gear mechanisms arranged in series. The hub transmission disclosed therein enables either a 7 speed shifting or a 14 speed shifting. The 14 speed hub transmission comprises five planetary gear mechanisms, the components of which can be selectively locked to establish the desired power transmission paths. A first planetary gear mechanism comprises a first sun gear rotatably supported by a hub axle which can be locked with the same. The first sun gear meshes with the smaller diameter of a two-step planetary gear which is rotatably supported by a first planetary gear carrier. The first planetary gear carrier is non-rotatably connected with the hub shell.

[0012] The large diameter of the two-step planetary gear meshes with a ring gear that can be locked either with the hub axle or the first sun gear.

[0013] A second planetary gear mechanism comprises a second sun gear rotatably supported by and lockable with the hub axle. Second planetary gears mesh with the sun gear and a second ring gear wherein the second ring gear is non-rotatably connected with the first sun gear.

[0014] A third planetary gear mechanism comprises a third sun gear which is rotatably supported by and lockable with the hub axle. Third planetary gears mesh with the third sun gears which are non-rotatably connected with the second planetary gears with the respective second planetary gears. The second sun gear meshes with the small diameter stage of the stepped planetary gears, and the third sun gear meshes with the large diameter stage of the stepped planetary gears.

[0015] The fourth and fifth planetary gear mechanisms are similar to the second and third planetary gear mechanisms and are symmetrically formed and arranged. The fourth and fifth planetary gear mechanisms therefore likewise comprise two-stage planetary gears, wherein the planetary gears of the second and third planetary gear mechanism and the planetary gears of the fourth and fifth planetary gear mechanisms are rotatably supported by means of a common planetary gear carrier. The small diameter stage of the stepped planetary gears of the fourth and fifth planetary gear mechanisms mesh with a ring gear that is non-rotatably connected with a driver.

[0016] A further embodiment of the 14-speed hub transmission is based on a modified embodiment of the afore described hub transmission and comprises a second ring gear which meshes with both small diameter stages of the symmetrically arranged stepped planetary gears. The common planetary gear carrier is replaced with two separate plantetary gear carriers wherein the planetary gear carrier of the second and third planetary gear mechanisms is non-rotatably connected with the first sun gear. The planetary gear carrier of the fourth and fifth planetary gear mechanisms is non-rotatably connected with the driver.

[0017] Owing to the increased number of clutches required for locking the separate components of the planetary gear mechanisms, for example the ring gears with the sun gears, the hub transmission according to DE 197 20 796 A1 is complicated and comparatively expensive.

[0018] It is an object of the invention to provide a hub transmission for a bicycle comprising a plurality of speed stages and enabling a lightweight and compact construction.

[0019] According to the invention, this object is accomplished by a hub transmission for a bicycle comprising the features of claim 1.

[0020] The invention is based on the idea of providing a hub transmission for a bicycle that comprises a hub axle, a driver and a hub shell each of which are rotatably supported by the hub axle. The hub transmission further comprises a power transmission mechanism that is disposed between the driver and the hub shell for transmitting rotational power from the driver to the hub shell through a plurality of power transmission paths, and a shift mechanism for selecting one of the plurality of power transmission paths. The power transmission mechanism comprises a plurality of planetary gear mechanisms, wherein a planetary gear carrier of a downstream planetary gear mechanism meshes with planetary gears of an upstream planetary gear mechanism. The downstream planetary gear mechanism comprises more than one sun gear.

[0021] A hub transmission formed in accordance with the invention has a number of advantages. Since the planetary gear carrier of the downstream planetary gear mechanism meshes with planetary gears of the upstream planetary gear mechanism a compact design is achieved that allows the realization of a plurality of power transmission paths while maintaining a small diameter of the hub. The aforementioned coupling of the downstream planetary gear carrier with upstream planetary gears further allows for a plurality of power transmission paths by means of a comparatively simple structure that reduces the risk of failure of components in the transmission.

[0022] Owing to the surprisingly simple structure of the inventive hub transmission, it is possible to produce a hub transmission that enables a comparatively great number of gear ratios at relatively low costs. Since the downstream planetary gear mechanism comprises more than one sun gear, the hub transmission according to the invention allows the implementation of 15 speed stages.

[0023] In a preferred embodiment, the power transmission mechanism comprises at least five planetary gear mechanisms that are arranged in series. Thereby it is possible to realize a 15-speed hub transmission with a compact design and a relatively small hub diameter.

[0024] Preferably the downstream planetary gear mechanism comprises first and second planetary gear mechanisms and the upstream planetary gear mechanism comprises at least third, fourth and fifth planetary gear mechanisms.

[0025] The first and second planetary gear mechanisms may comprise the planetary gear carrier of the downstream planetary gear mechanism. The fourth planetary gear mechanism may comprise the planetary gears of the upstream planetary gear mechanism. This means that the first and second planetary gear mechanisms are coupled with the fourth planetary gear mechanism by means of the planetary gear carrier of the downstream planetary gear mechanism which meshes with the upstream planetary gears.

[0026] Preferably the planetary gear carrier of the downstream planetary gear mechanism comprises a carrier portion and a ring gear portion which meshes with the planetary gears of the upstream planetary gear mechanism, wherein the carrier portion and the ring gear portion are non-rotatably connected, in particular integrally formed. Hence, it is to be emphasised that the planetary gear carrier of the downstream planetary gear mechanism fulfils two functions, namely a support function for the planetary gears of the first and second planetary gear mechanisms and a power transmission function for the planetary gears of the upstream planetary gear mechanism. Owing to the non-rotatable connection between the carrier portion and the ring gear portion, the compact design of the hub transmission is optimized.

[0027] Preferably the planetary gear carrier of the downstream planetary gear mechanism is connectable with the fifth planetary gear mechanism. Thereby, a number of further power transmission paths can be realized.

[0028] The connection of the planetary gear carrier and the downstream planetary gear mechanism with the fifth planetary gear mechanism can be realized, for example, by means of a preferred embodiment wherein the planetary gear carrier of the downstream planetary gear mechanism comprises a clutch engaging portion which is connectable with a planetary gear carrier of the fifth planetary gear mechanism.

[0029] To enable transmission of a rotational force from the planetary gear carrier of the downstream planetary gear mechanism to the hub shell, the planetary gear carrier of the downstream planetary gear mechanism is preferably connectable with the hub shell by means of a first clutch.

[0030] In a preferred embodiment, the first planetary gear mechanism further comprises a first sun gear rotatably supported by and lockable with the hub axle, a first ring gear coaxially arranged with the first sun gear and a plurality of first planetary gears meshing with the first sun gear and the first ring gear, wherein the first planetary gears are rotatably supported by the planetary gear carrier of the first planetary gear mechanism. The first planetary gear mechanism is part of the downstream planetary gear mechanism.

[0031] The second planetary gear mechanism may comprise a second sun gear rotatably supported by and lockable with the hub axle, a first ring gear coaxially arranged with the second sun gear and a plurality of second planetary gears meshing with the second sun gear and the first ring gear, wherein the second planetary gears are rotatably supported by the planetary gear carrier of the first planetary gear mechanism and the first and second planetary gears are non-rotatably connected, in particular integrally formed to form stepped planetary gears respectively. The second planetary gear mechanism is also part of the downstream planetary gear mechanism.

[0032] Thus, the downstream planetary mechanism comprises more than one sun gear, namely the first and second sun gears. The first and second sun gears of the downstream planetary gear mechanism (in general: the more than one sun gear) mesh with the planetary gears of the first and second planetary gear mechanisms and interact with the (common) planetary gear carrier of the downstream planetary gear mechanism.

[0033] Preferably the first ring gear is connectable with the hub shell by a second clutch for transmitting a rotational force from the first ring gear to the hub shell.

[0034] The third planetary gear mechanism may comprise a third sun gear rotatably supported by and lockable with the hub axle, a second planetary gear carrier rotatably supported relative to the hub axle and a plurality of third planetary gears rotatably supported by the second planetary gear carrier and meshing with the third sun gear.

[0035] The fourth planetary gear mechanism may comprise a fourth sun gear rotatably supported by and lockable with the hub axle, wherein the planetary gears of the upstream planetary gear mechanism, in particular the fourth planetary gear mechanism, are rotatably supported by the second planetary gear carrier and mesh with the fourth sun gear.

[0036] The planetary gears of the fourth planetary gear mechanism and the third planetary gears of the third planetary gear mechanism may be non-rotatably connected, in particular integrally formed to form stepped planetary gears respectively.

[0037] In a further preferred embodiment the fifth planetary gear mechanism comprises a fifth sun gear non-rotatably fixed to the hub axle, a second ring gear co-axially arranged with the fifth sun gear and a plurality of fifth planetary gears rotatably supported by a third planetary gear carrier, wherein the fifth planetary gears mesh with the fifth sun gear and the second ring gear.

[0038] The third planetary gear carrier can engage with the second planetary gear carrier.

[0039] A third clutch may be disposed between the third planetary gear carrier and the first planetary gear carrier, in particular the clutch engaging portion for transmitting a rotational force from the third planetary gear carrier to the first planetary gear carrier. A fourth clutch can be disposed between the driver and the second ring gear for transmitting a rotational force from the driver to the second ring gear. A fifth clutch may be disposed between the driver and the third planetary gear carrier for transmitting a rotational force from the driver to the third planetary gear carrier.

[0040] The invention will now be described by way of example with reference to the accompanying drawings in which:

Fig. 1

is a longitudinal cross-sectional view of a hub transmission according to an embodiment of the invention;

Fig. 2

is a longitudinal cross-sectional view of the hub transmission according to Fig. 1 in speed stage 1;

Fig. 3

is a longitudinal cross-sectional view of the hub transmission according to Fig. 1 in speed stage 2;

Fig. 4

is a longitudinal cross-sectional view of the hub transmission according to Fig. 1 in speed stage 3;

Fig. 5

is a longitudinal cross-sectional view of the hub transmission according to Fig. 1 in speed stage 4;

Fig. 6

is a longitudinal cross-sectional view of the hub transmission according to Fig. 1 in speed stage 5;

Fig. 7

is a longitudinal cross-sectional view of the hub transmission according to Fig. 1 in speed stage 6;

Fig. 8

is a longitudinal cross-sectional view of the hub transmission according to Fig. 1 in speed stage 7;

Fig. 9

is a longitudinal cross-sectional view of the hub transmission according to Fig. 1 in speed stage 8;

Fig. 10

is a longitudinal cross-sectional view of the hub transmission according to Fig. 1 in speed stage 9;

Fig. 11

is a longitudinal cross-sectional view of the hub transmission according to Fig. 1 in speed stage 10;

Fig. 12

is a longitudinal cross-sectional view of the hub transmission according to Fig. 1 in speed stage 11;

Fig. 13

is a longitudinal cross-sectional view of the hub transmission according to Fig. 1 in speed stage 12;

Fig. 14

is a longitudinal cross-sectional view of the hub transmission according to Fig. 1 in speed stage 13;

Fig. 15

is a longitudinal cross-sectional view of the hub transmission according to Fig. 1 in speed stage 14; and

Fig. 16

is a longitudinal cross-sectional view of the hub transmission according to Fig. 1 in speed stage 15;

[0041] Fig. 1 illustrates an embodiment of the hub transmission according to the invention that can be mounted to the rear wheel of a bicycle. The hub transmission comprises a hub axle 1 and a driver 2 which is rotatably supported by the hub axle 1. The hub transmission further comprises a hub shell 3 which is rotatably supported by the hub axle 1. A power transmission mechanism 4 is disposed between the driver 2 and the hub shell 3 for transmitting rotational power from the driver 2 to the hub shell 3 through a plurality of power transmission paths that can be selected to change the gear ratio as desired by the rider. To select one of the plurality of power transmission paths a shift mechanism 5 is provided.

[0042] The shift mechanism 5 corresponds to the shift mechanism described in detail in EP 1 323 627 A2 and US 6,607,465 B1 mentioned therein.

[0043] The power transmission mechanism 4 comprises a plurality of planetary gear mechanisms 6, 7, 8, 9, 10 including a downstream planetary gear mechanism and an upstream planetary gear mechanism wherein the upstream planetary gear mechanism is arranged closer to the driver 2 than the downstream planetary gear mechanism. As seen in the direction of the rotational power flow, the downstream planetary gear mechanism is arranged after the upstream planetary gear mechanism. For example, the downstream planetary gear mechanism comprises the first and second planetary gear mechanisms 6, 7 and the upstream planetary gear mechanism comprises the third, fourth and fifth planetary gear mechanism 8, 9, 10. The first and second planetary gear mechanisms 6, 7 (downstream planetary gear mechanism) can be coupled with the fourth planetary gear mechanism 9 (upstream planetary gear mechanism).

[0044] The plurality of planetary gear mechanisms 6, 7, 8, 9, 10 is arranged in series and comprises at least five planetary gear mechanisms 6, 7 ,8, 9, 10. The higher the number of the planetary gear mechanism 6, 7, 8, 9, 10 the closer it is arranged to the driver 2. For example, second planetary gear mechanism 7 is closer to the driver 2 than the first planetary gear mechanism 6.

[0045] As is evident from Fig. 1, the downstream planetary gear mechanism comprises a planetary gear carrier 31, and the upstream planetary gear mechanism comprises planetary gears 44 wherein the planetary gear carrier 31 of the downstream or first and second planetary gear mechanisms 6, 7 meshes with planetary gears 44 of the upstream or fourth planetary gear mechanism 8. The planetary gear carrier 31 is a common carrier for both the first and second planetary gear mechanisms 6, 7.

[0046] In general, the planetary gear carrier 31 has a longitudinally extending shape that is adapted to overlap components of the power transmission mechanism 4 that are arranged upstream of the first and second planetary gear mechanisms 6, 7 and, thus, more proximate to the driver 2 than the downstream planetary gear mechanism 6, 7.

[0047] In particular, the planetary gear carrier 31 of the downstream planetary gear mechanism 6, 7 axially extends from the area of the downstream or first and second planetary gear mechanisms 6, 7 to the area of the upstream or fourth planetary gear mechanism 9. As illustrated in Fig. 1, the planetary gear carrier 31 axially extends over more than 1/3 to 1/2 of the entire length of the hub transmission. The axial extension of the planetary gear carrier 31 is such that the third planetary gear mechanism 8 which is arranged between the downstream planetary gear mechanisms 6, 7 and the upstream, in particular fourth planetary gear mechanism 9 is overlapped by the planetary gear carrier 31. In the embodiment according to Fig. 1, the third planetary gear mechanism 8 is not engaged with the planetary gear carrier 31.

[0048] The planetary gear carrier 31 comprises a stepped shape wherein the inner diameter of the subsequent steps increases towards the driver 2. The stepped shape of the planetary gear carrier 31 will be described in more detail in conjunction with the respective components associated thereto.

[0049] The planetary gear carrier 31 further comprises a (first) clutch engaging portion 31 c which is arranged on the axial end of the planetary gear carrier 31 proximate to the driver 2. The clutch engaging portion 31 c is provided to engage with/disengage from a clutch 53 (third clutch) which will be described in more detail in connection with the fifth planetary gear mechanism 10.

[0050] The planetary gear carrier 31 further comprises a ring gear portion 31b. The ring gear portion 31b is integrally connected with the clutch engaging portion 31c and is formed with a smaller inner diameter than clutch engaging portion 31 c. The ring gear portion 31b meshes with the planetary gears 44 of the upstream or fourth planetary gear mechanism 9. The inner diameter of the ring gear portion 31b is larger than the outer diameter of third planetary gears 43 of the third planetary gear mechanism 8, to avoid engagement or collision therewith.

[0051] The ring gear portion 31 b is integrally connected with a carrier portion 31a which supports first planetary gears 41 of the first downstream planetary gear mechanism 6 and second planetary gears 42 of the second downstream planetary gear mechanism 7. The first planetary gears 41 are rotatably supported by first planetary gear shafts 41 a. The second planetary gears 42 are rotatably supported by second planetary gear shafts 42a. The first and second planetary gear shafts 41 a, 42a are disposed in a carrier portion 31a of the planetary gear carrier 31. Typically, three or more first planetary gears 41 respectively second planetary gears 42 are provided in the first respectively second planetary gear mechanism 6, 7.

[0052] A further (or second) clutch engaging portion 31d is integrally formed with the carrier portion 31a and is provided for engaging with/disengaging from a first clutch 51 to establish/interrupt a power transmission from the planetary gear carrier 31 to the hub shell 3. The further (or second) clutch engaging portion 31d is arranged downstream of the first planetary gear mechanism 6. The ring gear portion 31b and the (first) clutch engaging portion 31c are located upstream of the planetary gear mechanism 6. Again, the downstream or upstream arrangement of components is seen and to be understood in the direction of the power flow.

[0053] The plurality of planetary gear mechanisms 6, 7, 8, 9, 10 will be described in the following.

[0054] The first planetary gear mechanism 6 is arranged most downstream or most distant from the driver 2 and comprises a first sun gear 11 which is rotatably supported by and lockable with the hub axle 1. Between an inner peripheral surface of the first sun gear 11 and the hub axle 1, a first sun gear guide ring 61 is non-rotatably fixed to the hub axle 1. The first sun gear guide ring 61 allows the locking and unlocking of the first sun gear 11 by means of the shifting mechanism 5.

[0055] The plurality of first planetary gears 41 is rotatably supported by the first planetary gear carrier 31, in particular by first planetary gear shafts 41a disposed in the first planetary gear carrier 31, and meshes with the first sun gear 11.

[0056] The second planetary gear mechanism 7 is arranged upstream of the first planetary gear mechanism 6 and comprises a second sun gear 12 which is rotatably supported by, and lockable with, the hub axle 1.

[0057] As seen in Fig. 1, the first sun gear 11 and the second sun gear 12 (in general: the more than one or at least two sun gears) are arranged adjacent or next to each other.

[0058] The first and second sun gears 11, 12 (in general: the more than one or at least two sun gears) are lockable with the hub axle 1.

[0059] The first sun gear 11 and the second sun gear 12 form part of the downstream planetary gear mechanism which is coupled with the planetary gears 44 of the upstream planetary gear mechanism or fourth planetary gear mechanism 9, by means of the first planetary gear carrier 31.

[0060] As further seen in Fig. 1, the second sun gear 12 comprises an axial projection 12a which extends in a downstream axial direction. The axial projection 12a is arranged radially below the engaging portion of the first sun gear 11 which meshes with the first planetary gears 41. To this end, the sun gear 11 comprises a shoulder which accommodates the axial projection 12a of the second sun gear 12. Thereby, a compact and stable configuration of the first and second sun gears 11, 12 is achieved.

[0061] The second planetary gear mechanism 7 further comprises the second planetary gears 42 which mesh with second sun gear 12, Coaxially arranged in relation to and rotatably supported by the hub axle 1, is a first ring gear 21 which meshes with second planetary gears 42 of the second planetary gear mechanism 7 such that the second planetary gears 42 are arranged in between the first ring gear 21 and the second sun gear 12. The second planetary gears 42 are supported by second planetary gear shafts 42a. The second planetary gear shafts 42a are disposed in the first planetary gear carrier 31.

[0062] The second planetary gear shaft 42a is integrally formed with the first planetary gear shaft 41 a such that the first and second planetary gears 41, 42 are supported by the same or a common shaft 41 a, 42a.

[0063] As illustrated in Fig. 1, the first and second planetary gears 41, 42 form two gear stages wherein the large diameter gear stage of the first planetary gear 41 meshes with the first sun gear 11 and the small diameter gear stage of the second planetary gear 42 meshes with the first ring gear 21. The small diameter gear stage of the second planetary gears 42 is arranged proximate to the third planetary gear mechanism 8. The first and second planetary gears 41, 42 are non-rotatably coupled, in particular integrally formed.

[0064] Thereby, the first and second planetary gears 41, 42 constitute a stepped or non-rotatably coupled planetary gear comprising two different diameters, which mesh with the first and second sun gears 11, 12 (in general: with the at least two sun gears 11,12). The large diameter of the stepped planetary gear meshes with the first sun gear 11 and the small diameter of the stepped planetary gear meshes with the second sun gear 12 and the first ring gear 21.

[0065] The at least two sun gears 11, 12 can be coupled by means of the first planetary gear carrier 31 with an upstream planetary gear mechanism, in particular with the fourth planetary gear mechanism 9.

[0066] The first ring gear 21 can be connected with or disconnected from the hub shell 3 by means of a second (one-way) clutch 52 which is disposed between the first ring gear 21 and the hub shell 3.

[0067] As described above, the ring gear carrier 31 of the first planetary gear mechanism 6 extends axially beyond the first and second planetary gears 41, 42 in a longitudinal direction of the hub transmission thereby overlapping at least the subsequently arranged upstream third and fourth planetary gear mechanisms 8, 9. The outer contour of first planetary gear carrier 31 is adapted to partially accommodate the first ring gear 21 and forms a shoulder 31e such that the first ring gear 21 is arranged between the shoulder 31e and the large diameter gear stage of the first planetary gears 41.

[0068] The third planetary gear mechanism 8 is located upstream of the second planetary gear mechanism 7 and comprises a third sun gear 13 which is rotatably supported by and lockable with the hub axle 1. Between an inner surface of the second sun gear 13 and the hub axle 1, a third sun gear guide ring 63 is non-rotatably fixed to the hub axle 1. A plurality of third planetary gears 43 is rotatably supported by a second planetary gear carrier 32 which is rotatably supported by the hub axle 1. To this end, the third planetary gears 43 are rotatably supported by third planetary gear shafts 43a which are supported by second planetary gear carrier 32. Typically three or more third planetary gears 43 are provided.

[0069] The fourth planetary gear mechanism 8 is arranged upstream of the third planetary gear mechanism 8 and comprises a fourth sun gear 14 which is rotatably supported by, and lockable with, the hub axle 1. Between an inner peripheral surface of the fourth sun gear 13 and the hub axle 1, a fourth sun gear guide ring 64 is arranged and non-rotatably fixed to hub axle 1. The fourth sun gear guide ring 64 can be actuated by means of the shifting mechanism 5 to lock/unlock the fourth sun gear 14.

[0070] A plurality of fourth planetary gears 44 meshes with the fourth sun gear 14 and is rotatably supported by the second planetary gear carrier 32. In particular, fourth planetary gears 44 are arranged on a fourth planetary gear shaft 44a which is integrally formed with the third planetary gear shaft 43a and, thus, represents a common planetary gear shaft for the third and fourth planetary gears 43, 44.

[0071] As is evident from Fig. 1, third and fourth planetary gears 43, 44 are non-rotatably connected and integrally form a stepped planetary gear 402. The small diameter gear stage of the stepped planetary gear 402 (third planetary gears 43) meshes with the third sun gear 13, and the large diameter gear stage of the stepped planetary gear 402 (fourth planetary gears 44) meshes with the fourth sun gear 9. Moreover, the large diameter gear stage of the stepped planetary gear 402 (fourth planetary gears 44) meshes with the ring gear portion 31b of the downstream planetary gear carrier 31. Thus, it is possible to establish a transmission path connecting the fourth sun gear 9 with the first planetary gear carrier 31.

[0072] A fifth planetary gear mechanism 10 is arranged upstream of the fourth planetary gear mechanism 9 and represents the planetary gear mechanism closest to the driver 2. The fifth planetary gear mechanism 10 comprises a fifth sun gear 15 which is non-rotatably fixed to the hub axle 1. A second ring gear 22 is coaxially arranged with and rotatably supported by the hub axle 1. Between the second ring gear 22 and the fifth sun gear 15 a plurality of fifth planetary gears 45 is arranged which are formed as two-step planetary gears. The large diameter gear stage of the fifth planetary gears 45 meshes with the second ring gear 22, and the small diameter gear stage of the fifth planetary gears 45 meshes with the fifth sun gear 15. Typically three or more fifth planetary gears 45 are provided.

[0073] The fifth planetary gears 45 are rotatably supported by a third planetary gear carrier 33 which can rotate around the hub axle 1. The third planetary gear carrier 33 comprises fifth planetary gear shafts 45a which rotatably support the fifth planetary gears 45. The third planetary gear carrier 33 is engaged with the second planetary gear carrier 32 to transmit power from the third planetary gear carrier 33 to the second planetary gear carrier 32.

[0074] As is readily apparent from Fig. 1, the middle axes of the third and fourth planetary gear shafts 43a, 44a and the middle axes of the fifth planetary gear shafts 45a are radially spaced apart. The middle axes of fifth planetary gear shafts 45a are arranged on a cylindrical plane having a larger diameter than a cylindrical plane which comprises the middle axes of the third and fourth planetary gear shafts 43a, 44a. The cylindrical plane which comprises the middle axes of first and second planetary gear shafts 41 a, 42a corresponds to the cylindrical plane of the middle axes of the fifth planetary gear shafts 45a. Thus, the middle axes of the third and fourth planetary gear shafts 43a, 44a, which are arranged between the second and fifth planetary gear mechanisms 7 and 10, are closer to the hub axle 1 than the middle axes of the second and fifth planetary gear shafts 42a, 45a, respectively.

[0075] The third planetary gear carrier 33 of the fifth planetary gear mechanism 9 can be connected to the downstream planetary gear carrier 31. For this purpose, the third clutch 53 mentioned above is provided between the third planetary gear carrier 33 and the first planetary gear carrier 31. In particular, the third clutch 53 is arranged at an end of the third planetary gear carrier 33 distant from the driver 2 and engages with/disengages from the clutch engaging portion 31c of downstream of the first planetary gear carrier 31. For the power transmission from the driver 2 to the fifth planetary gear mechanism 9, fourth and fifth clutches 54 and 55 are provided.

[0076] The fourth clutch 54 is a one-way clutch disposed between the driver 2 and the second ring gear 22. The second ring gear 22 comprises an axial projection 22a which extends towards the driver 2. The axial projection 22a comprises on its inner peripheral surface a clutch engaging portion 22b, which cooperates with the fourth clutch 54 to lock or unlock the second ring gear 22 with the driver 2. The fourth clutch 54 is supported by an axial projection 2a of the driver 2 that extends in parallel with the axial projection 22a of the ring gear 22.

[0077] For speed stages 1 to 6, the fourth clutch 54 is engaged with the ring gear 22 to transmit power from the driver 2 to the ring gear 22.

[0078] For speed stages 7 to 11, a fifth clutch 55 is provided which is disposed between the driver 2 and the third planetary gear carrier 33 for transmitting rotational power from the driver 2 to the third planetary gear driver 33. The fifth clutch 55 is formed as a clutch ring and is axially movable in a longitudinal direction of the hub axle 1. The fifth clutch 55 comprises two engaging portions 55a, 55b which are adapted to engage with clutch engaging portions 2b and 33a which are provided on the driver 2 and the third planetary gear carrier 33, respectively.

[0079] The clutch engaging portion 2b of the driver 2 is formed on the inner peripheral surface of the axial projection 2a and engages with the upper or radial engaging portion 55b of the fifth clutch 55. The clutch engaging portion 33a of the third planetary gear carrier 33 is adapted to engage with/disengage from the lower or axial engaging portion 55a of the fifth clutch 55.

[0080] For speed stages 7 to 11, the axial engaging portion 55a of the fifth clutch 55 and the clutch engaging portion 33a of the third planetary gear carrier 33 are coupled and the fourth clutch 54 is uncoupled.

[0081] A more detailed description of the aforementioned clutch mechanism including the fourth and fifth clutches 54 and 55 is disclosed in EP 1 323 627 A2 as well as in European Patent Application 07 001 076.4, both owned by the applicant.

[0082] The function of the hub transmission according to Fig. 1 is explained with reference to Figures 2 to 16 in which the coupling of the various components for each speed stage and the specific power transmission path realized thereby are illustrated. The bold lines and arrows indicated in Figures 2 to 16 illustrate the rotational power flow through the power transmission mechanism 4. The coupling of the various components as well as the power transmission paths are indicated in the following Tables 1 and 2 wherein Table 1 concerns the coupling of the components and Table 2 concerns the specific power transmission path.

Table 1

Speed Stage	Clutch ring 55 (Driver and 3rd Planetary gear carrier 33)	First Sun gear 11	Second Sun gear 12	Third Sun gear 13	Fourth Sun gear 14
1	Disengaged	Free	Free	Free	Free
2	Disengaged	Locked	Free	Free	Free
3	Disengaged	Free	Free	Free	Locked
4	Disengaged	Free	Free	Locked	Free
5	Disengaged	Locked	Free	Free	Locked
6	Disengaged	Locked	Free	Locked	Free
7	Disengaged	Free	Locked	Free	Locked
8	Disengaged	Free	Locked	Locked	Free
9	Engaged	Locked	Free	Free	Free
10	Engaged	Free	Free	Free	Locked
11	Engaged	Free	Free	Locked	Free
12	Engaged	Locked	Free	Free	Locked
13	Engaged	Locked	Free	Locked	Free
14	Engaged	Free	Locked	Free	Locked
15	Engaged	Free	Locked	Locked	Free

Table 2

Speed Stage	power Transmission Path	Gear ratio
1	Driver - 4th clutch 54 - 2nd ring gear 22 - (5th planet gear 45 rotates around 5th sun gear 15)-3rd planetary gear carrier 33 - 3rd clutch 53 - 1st planetary carrier 31 - 1st clutch 51 - Hub Shell	0.426
2	Driver - 4th clutch 54 - 2nd ring gear 22 - (5th planet gear 45 rotates around 5th sun gear 15) - 3rd planetary gear carrier 33 - 3rd clutch 53 - 1st planetary carrier 31 - (1st planet gear 41 rotates around 1st sun gear 11) - 1st ring gear 21 - 2nd clutch 52 - Hub Shell	0.545
3	Driver - 4th clutch 54 - 2nd ring gear 22 - (5th planet gear 45 rotates around 5th sun gear 15) - 3rd planetary gear carrier 33 - 2nd planetary gear carrier 32 - (4th planet gear 44 rotates around 4th sun gear 14) - 1st planetary gear carrier 31 - 1st clutch 51 - Hub Shell	0.612
4	Driver - 4th clutch 54 - 2nd ring gear 22 - (5th planet gear 45 rotates around 5th sun gear 15) - 3rd planetary gear carrier 33 - 2nd planetary gear carrier 32 - (3rd planet gear 43 rotates around 3rd sun gear 13) - 1st planetary gear carrier 31 - 1st clutch 51 - Hub Shell	0.694
5	Driver - 4th clutch 54 - 2nd ring gear 22 - (5th planet gear 45 rotates around 5th sun gear 15) - 3rd planetary gear carrier 33 - 2nd planetary gear carrier 32 - (4th planet gear 44 rotates around 4th sun gear 14) - 1st planetary carrier 31 - (1st planet gear 41 rotates around 1st sun gear 11) - 1st ring gear 21 - 2nd clutch 52 - Hub Shell	0.782
6	Driver - 4th clutch 54 - 2nd ring gear 22 - (5th planet gear 45 rotates around 5th sun gear 15) - 3rd planetary gear carrier 33 - 2nd planetary gear carrier 32 - (3rd planet gear 43 rotates around 3rd sun gear 13) - 1st planetary carrier 31 - (1st planet gear 41 rotates around 1st sun gear 11) - 1st ring gear 21 - 2nd clutch 52 - Hub Shell	0.887
7	Driver - 4th clutch 54 - 2nd ring gear 22 - (5th planet gear 45 rotates around 5th sun gear 15) - 3rd planetary gear carrier 33 - 2nd planetary gear carrier 32 - (4th planet gear 44 rotates around 4th sun gear 14) - 1st planetary carrier 31 - (2nd planet gear 42 rotates around 2nd sun gear 12) - 1st ring gear 21 - 2nd clutch 52 - Hub Shell	0.997
8	Driver - 4th clutch 54 - 2nd ring gear 22 - (5th planet gear 45 rotates around 5th sun gear 15) - 3rd planetary gear carrier 33 - 2nd planetary gear carrier 32 - (3rd planet gear 43 rotates around 3rd sun gear 13) - 1st planetary carrier 31 - (2nd planet gear 42 rotates around 2nd sun gear 12) - 1st ring gear 21 - 2nd clutch 52 - Hub Shell	1.130
9	Driver - 5th clutch 55 - 3rd planetary gear carrier 33 - 3rd clutch 53 - 1st planetary carrier 31 - (1st planet gear 41 rotates around 1st sun gear 11) - 1st ring gear 21 - 2nd clutch 52 - Hub Shell	1.279
10	Driver - 5th clutch 55 - 3rd planetary gear carrier 33 - 2nd planetary gear carrier 32 - (4th planet gear 44 rotates around 4th sun gear 14) - 1st planetary gear carrier 31 - 1st clutch 51 - Hub Shell	1.437
11	Driver - 5th clutch 55 - 3rd planetary gear carrier 33 - 2nd planetary gear carrier 32 - (3rd planet gear 43 rotates around 3rd sun gear 13) - 1st planetary gear carrier 31 - 1st clutch 51 - Hub Shell	1.630
12	Driver - 5th clutch 55 - 3rd planetary gear carrier 33 - 2nd planetary gear carrier 32 - (4th planet gear 44 rotates around 4th sun gear 14) - 1st planetary carrier 31 - (1st planet gear 41 rotates around 1st sun gear 11) - 1st ring gear 21 - 2nd clutch 52 - Hub Shell	1.838
13	Driver - 5th clutch 55 - 3rd planetary gear carrier 33 - 2nd planetary gear carrier 32 - (3rd planet gear 43 rotates around 3rd sun gear 13) - 1st planetary carrier 31 - (1st planet gear 41 rotates around 1st sun gear 11) - 1st ring gear 21 - 2nd clutch 52 - Hub Shell	2.085
14	Driver - 5th clutch 55 - 3rd planetary gear carrier 33 - 2nd planetary gear carrier 32 - (4th planet gear 44 rotates around 4th sun gear 14) - 1st planetary carrier 31 - (2nd planet gear 42 rotates around 2nd sun gear 12) - 1st ring gear 21 - 2nd clutch 52 - Hub Shell	2.341
15	Driver - 5th clutch 55 - 3rd planetary gear carrier 33 - 2nd planetary gear carrier 32 - (3rd planet gear 43 rotates around 3rd sun gear 13) - 1st planetary carrier 31 - (2nd planet gear 42 rotates around 2nd sun gear 11) - 1st ring gear 21 - 2nd clutch 52 - Hub Shell	2.656

[0083] In summary, the hub transmission according to the described embodiment of the invention allows the realization of an 11 speed internal hub transmission wherein the diameter of the hub shell 2 is similar to the diameter of a currently available 8 speed hub transmission. This means that the hub transmission of the invention provides more speed stages than the conventional hub transmission without increasing the hub diameter. Moreover, the hub transmission according to Fig. 1 provides the advantage that all transmission paths are simple which leads to an efficient power transmission. In general, the planetary gear carrier 31 of the downstream planetary gear mechanism 6 has an axially elongated shape adapted to mesh with the planetary gears 43 of the upstream planetary gear mechanism 8. Moreover, the axially elongated shape of the planetary gear carrier 31 allows for coupling/uncoupling the planetary gear carrier 31 with/from a planetary gear carrier 33 of a further upstream planetary gear mechanism 9. In particular, the axially elongated planetary gear carrier 31 of the downstream planetary gear mechanism 6 is adapted to selectively transmit rotational power from the planetary gears 43 of an upstream planetary gear mechanism 8 and to selectively transmit rotational power from the planetary gear carrier 33 of the further upstream planetary gear mechanism 9.

[0084] The axially elongated shape of the downstream planetary gear carrier 31 allows for a compact, small diameter internal hub transmission for a bicycle with highly efficient transmission paths.

Reference signs

[0085] 

1

hub axle

2

driver

3

hub shell

4

power transmission mechanism

5

shift mechanism

6, 7, 8, 9, 10

planetary gear mechanisms

11

1^st sun gear

12

2^nd sun gear

12a

axial projection

13

3^rd sun gear

14

4^th sun gear

15

5^th sun gear

21

1^st ring gear

22

2^nd ring gear

22a

axial projection

22b

clutch engaging portion

31

1^st planetary gear carrier

31a

carrier portion

31b

ring gear portion

31 c

clutch engaging portion

31 d

clutch engaging portion

31e

shoulder

32

2^nd planetary gear carrier

33

3^rd planetary gear carrier

33a

clutch engaging portion

41

1^st planetary gear

41a

1^st planetary gear shaft

42

2^nd planetary gear

42a

2^nd planetary gear shaft

43

3^rd planetary gear

43a

3^rd planetary gear shaft

44

4^th planetary gear

44a

3^rd planetary gear shaft

45

5^th planetary gear

45a

5^th planetary gear shaft

51

1^st one-way clutch

52

2^nd one-way clutch

53

3^rd one-way clutch

54

4^th one-way clutch

55

5^th clutch

61

1^st sun gear guide ring

62

2^nd sun gear guide ring

63

3^rd sun gear guide ring

64

4^th sun gear guide ring

402

stepped planetary gears

Claims

1. A hub transmission for a bicycle comprising:

- a hub axle (1);

- a driver (2) rotatably supported by the hub axle (1);

- a hub shell (3) rotatably supported by the hub axle (1);

- a power transmission mechanism (4) disposed between the driver (2) and the hub shell (3) for communicating rotational power from the driver (2) to the hub shell (3) through a plurality of power transmission paths; and

- a shift mechanism (5) for selecting one of the plurality of power transmission paths;

wherein the power transmission mechanism (4) comprises a plurality of planetary gear mechanisms (6, 7, 8, 9, 10)
characterized in that
a planetary gear carrier (31) of a downstream planetary gear mechanism meshes with planetary gears (44) of an upstream planetary gear mechanism, wherein the downstream planetary gear mechanism comprises more than one sun gear.

2. The hub transmission according to claim 1,
wherein the power transmission mechanism (4) comprises at least five planetary gear mechanisms (6, 7, 8, 9, 10) that are arranged in series.

3. The hub transmission according to claim 1 or 2;
wherein the downstream planetary gear mechanism comprises first and second planetary gear mechanisms (6, 7) and the upstream planetary gear mechanism comprises at least third, fourth and fifth planetary gear mechanisms (8, 9, 10).

4. The hub transmission according to claim 3,
wherein the first and second planetary gear mechanisms (6, 7) comprise the planetary gear carrier (31) of the downstream planetary gear mechanism and the fourth gear mechanism (9) comprises the planetary gears (44) of the upstream planetary gear mechanism.

5. The hub transmission according to any of claims 1 to 4,
wherein the planetary gear carrier (31) of the downstream planetary gear mechanism comprises a carrier portion (31a) and a ring gear portion (31b) which meshes with the planetary gears (44) of the upstream planetary gear mechanism, wherein the carrier portion (31a) and the ring gear portion (31b) are non-rotatably connected, in particular integrally formed.

6. The hub transmission according to any of claims 3 to 5,
wherein the planetary gear carrier (31) is connectable with the fifth planetary gear mechanism (10).

7. The hub transmission according to claim 6,
wherein the planetary gear carrier (31) comprises a clutch engaging portion (31c) which is connectable with a planetary gear carrier (33) of the fifth planetary gear mechanism (10).

8. The hub transmission according to any of claims 1 to 7,
wherein the planetary gear carrier (31) is connectable with the hub shell (3) by means of a first clutch (51) for transmitting a rotational force from the planetary gear carrier (31) to the hub shell (3).

9. The hub transmission according to any of claims 3 to 8,
wherein the first planetary gear mechanism (6) comprises a first sun gear (11) rotatably supported by and lockable with the hub axle (1), and a plurality of first planetary gears (41) meshing with the first sun gear (11), wherein the first planetary gears (41) are rotatably supported by the planetary gear carrier (31) of the first planetary gear mechanism (6).

10. The hub transmission according to any of claims 3 to 9,
wherein the second planetary gear mechanism (7) comprises a second sun gear (12) rotatably supported by and lockable with the hub axle (1), a first ring gear (21) coaxially arranged with the second sun gear (12) and a plurality of second planetary gears (42) meshing with the second sun gear (12) and the first ring gear (21), wherein the second planetary gears (31) are rotatably supported by the planetary gear carrier (31) of the first planetary gear mechanism (6) and the first and second planetary gears (41, 42) are non-rotatably connected, in particular integrally formed to form stepped planetary gears respectively.

11. The hub transmission according to claim 10,
wherein the first ring gear (21) is connectable with the hub shell (3) by a second clutch (52) for transmitting a rotational force from the first ring gear (21) to the hub shell (3).

12. The hub transmission according to any of claims 3 to 11,
wherein the third planetary gear mechanism (8) comprises a third sun gear (13) rotatably supported by and lockable with the hub axle (1), a second planetary gear carrier (32) rotatably supported relative to the hub axle (1) and a plurality of third planetary gears (43) rotatably supported by the second planetary gear carrier (32) and meshing with the third sun gear (13).

13. The hub transmission according to any of claims 3 to 12,
wherein the fourth planetary gear mechanism (9) comprises a fourth sun gear (14) rotatably supported by and lockable with the hub axle (1) wherein the planetary gears (44) of the upstream planetary gear mechanism, in particular of the fourth planetary gear mechanism (9) are rotatably supported by the second planetary gear carrier (32) and mesh with the fourth sun gear (14).

14. The hub transmission according to claim 13,
wherein the planetary gears (44) of the fourth planetary gear mechanism (9) and the third planetary gears (43) of the third planetary gear mechanism (8) are non-rotatably connected, in particular integrally formed, to form stepped planetary gears (402) respectively.

15. The hub transmission according to any of claims 3 to 14,
wherein the fifth planetary gear mechanism (10) comprises a fifth sun gear (15) non-rotatably fixed to the hub axle (1), a second ring gear (22) coaxially arranged with the fifth sun gear (15) and a plurality of fifth planetary gears (45) rotatably supported by a third planetary gear carrier (33) wherein the fifth planetary gears (45) mesh with the fifth sun gear (15) and the second ring gear (22).

16. The hub transmission according to claim 15,
wherein the third planetary gear carrier (33) engages with the second planetary gear carrier (32).

17. The hub transmission according to claim 15 or 16,
wherein a third clutch (53) is disposed between the third planetary gear carrier (33) and the first planetary gear carrier (31), in particular the clutch engaging portion (31c) for transmitting a rotational force from the third planetary gear carrier (33) to the first planetary gear carrier (31).

18. The hub transmission according to any of claims 12 to 17,
wherein a fourth clutch (54) is disposed between the driver (2) and the second ring gear (22) for transmitting a rotational force from the driver (2) to the second ring gear (22).

19. The hub transmission according to any of claims 13 to 18,
wherein a fifth clutch (55) is disposed between the driver (2) and the third planetary gear carrier (33) for transmitting a rotational force from the driver (2) to the third planetary gear carrier (33).

Drawing